Diagnostic yield of axillary artery ultrasound in addition to temporal artery ultrasound for the diagnosis of giant cell arteritis.

OBJECTIVES: There are limited data on the additional diagnostic yield of axillary artery ultrasound (axUS) in addition to temporal artery ultrasound (tempUS) for the diagnosis of giant cell arteritis (GCA). METHODS: Retrospective study of consecutive patients with suspected GCA who underwent a standardized axUS and tempUS between 01/2015 and 03/2017. The diagnostic yield of axUS in addition to ultrasound of the temporal arteries with respect to the final clinical diagnosis was assessed, with a positive axUS defined as circumferential, hypoechogenic thickening of the far wall axillary artery intima media thickness (axIMT) ≥1.3 mm. A subgroup of patients underwent PET-CT within one week before or after the sonographic study. Separate analyses were performed regarding certain subgroups according to clinical presentation and to clinical pre-test probability for cranial GCA. RESULTS: Out of 228 patients, 92 received a final diagnosis of GCA. From the 92 patients with a final diagnosis of GCA, 50 (54.3%), 13 (14.1%) and 15 (16.3%) had a positive tempUS, positive axUS, and combined positive tempUS and axUS, respectively. The sensitivity of sonographic imaging for the final diagnosis of GCA increased from 69.6% to 84.8%, when axUS results were considered in addition to tempUS, while the specificity remained high (no false positive axUS). The diagnostic yield of axUS was highest in patients with a low clinical probability of cranial GCA and lowest in patients with symptoms of ocular ischemia. We observed a substantial rate (42.1%) of discordant results between axUS and PET-CT in a subgroup of 38 patients. CONCLUSIONS: In conclusion, axUS offers a substantial diagnostic yield in addition to tempUS in subjects with suspected GCA, mainly in those subjects with low clinical probability for cranial GCA.